Not applicable.
The present invention relates to ink jet printing and in particular discloses a shape memory alloy ink jet printer.
The present invention further relates to the field of drop on demand ink jet printing.
Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.
In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.
Many different techniques on ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, xe2x80x9cNon-Impact Printing: Introduction and Historical Perspectivexe2x80x9d, Output Hard Copy Devices, Editors R. Dubeck and S Sherr, pages 207-220 (1988).
Ink Jet printers themselves come in many different types. The utilisation of a continuous stream ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.
U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electrostatic field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by, Sweet et al)
Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.
Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.
As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.
It is an object of the present invention to provide for a new form of ink jet printing device that utilizes a shape memory alloy in its activation method.
In accordance with a first aspect of the present invention there is provided a method of ejecting ink from a chamber comprising the steps of: a) providing a cantilevered beam actuator incorporating a shape memory alloy; and b) transforming said shape memory alloy from its martensitic phase to its austenitic phase or vice versa to cause the ink to eject from said chamber. Further, the actuator comprises a conductive shape memory alloy panel in a quiescent state and which transfers to an ink ejection state upon heating thereby causing said ink ejection from the chamber. Preferably, the heating occurs by means of passing a current through the shape memory alloy. The chamber is formed from a crystallographic etch of a silicon wafer so as to have one surface of the chamber substantially formed by the actuator. Advantageously, the actuator is formed from a conductive shape memory alloy arranged in a serpentine form and is attached to one wall of the chamber opposite a nozzle port from which ink is ejected. Further, the nozzle port is formed by the back etching of a silicon wafer to the epitaxial layer and etching a nozzle port hole in the epitaxial layer. The crystallographic etch includes providing side wall slots of non-etched layers of a processed silicon wafer so as to the extend the dimensions of the chamber as a result of the crystallographic etch process. Preferably, the shape memory alloy comprises nickel titanium alloy.